Geodesic
Logarithmically absolutely monotone trigonometric functions
Zapiski Nauchnykh Seminarov POMI, Investigations on linear operators and function theory. Part 49, Tome 503 (2021), pp. 57-71 
O. L. Vinogradov. Logarithmically absolutely monotone trigonometric functions. Zapiski Nauchnykh Seminarov POMI, Investigations on linear operators and function theory. Part 49, Tome 503 (2021), pp. 57-71. http://geodesic.mathdoc.fr/item/ZNSL_2021_503_a2/
@article{ZNSL_2021_503_a2,
     author = {O. L. Vinogradov},
     title = {Logarithmically absolutely monotone trigonometric functions},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {57--71},
     year = {2021},
     volume = {503},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2021_503_a2/}
}
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Voir la notice du chapitre de livre provenant de la source Math-Net.Ru

We study absolute monotonicity and logarithmic absolute monotonicity for functions $$ f(z)=\dfrac{\cos{\alpha_1z}\cdot\ldots\cdot\cos{\alpha_Mz} \cdot\sin{\beta_1z}\cdot\ldots\cdot\sin{\beta_Nz}} {\cos{\alpha'_1z}\cdot\ldots\cdot\cos{\alpha'_{M'}z} \cdot\sin{\beta'_1z}\cdot\ldots\cdot\sin{\beta'_{N'}z}}z^{N'-N}. $$ Here $N,M,N',M'\in\Bbb Z_+$, $\alpha_j,\alpha_j',\beta_j,\beta_j'\geqslant 0$; if $\beta=0$, then the factor $\sin{\beta z}$ is replaced by $z$; if $N,M,N'$, or $M'$ equals zero, then the corresponding factors are absent. A criterion of logarithmic absolute monotonicity for $f$ is obtained. We give some applications of absolute monotonicity to sharp inequalities for derivatives and differences of trigonometric polynomials and entire functions of exponential type.

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